Experimental Investigation Of The Straw Pre-treatment To Enhance Its High Solid Anaerobic Digestion

About 0.7 billion tons of straw is produced every year in China,50%of which is not processed and utilized,consequently leading to a large resource waste.Straw treatment with anaerobic digestion is an ideal technology which can give attention to both energy and environmental protection simultaneously, but the complicated and compact molecular configuration of straw causes huge inefficiency of anaerobic digestion.The various pretreatment methods were compared.In first,sodium hydroxide,ammonia was used to treatment of wheat straw,to analyze main components change.The results showed that the pretreatment by sodium hydroxide had the highest removal of cellulose,with removal of cellulose, hemicelluloses,lignin up to 17.42%,35.24%and 24.09%.It can be concluded from the experiment that thermo-sodium hydroxide pretreatment is more effective than sodium hydroxide pretreatment respectively.The limiting factors of orthogonal experiment,such as the concentration of sodium hydroxide,the temperature and time of pretreatment, were evaluated.Cumulative biogas production after sodium hydroxide pretreatment at 85℃was about 15.43%more than at 25℃room temperature and about 26.46%more than non-pretreatment.The celluloses extracted from untreated and thermo-sodium hydroxide pretreated wheat straws were characterized by Fourier Transform Infrared Spectrophotometry(FTIR-spectra) and Scanning Electron Microscope(SEM).The results showed that significant changes have occurred in the morphology of the thermo-sodium hydroxide pretreated cellulose fibers.The optimum condition of NaOH/H₂O₂ pretreatment of the wheat straw was studied through orthogonal experiment.The limiting factors,such as the concentration of NaOH and H₂O₂,and pretreatment time,were optimized.The results showed that optimum parameters of NaOH/H₂O₂ pretreatment were: the concentration of NaOH was 2%,the concentration of H₂O₂ was 1%,and pretreatment time was 12 hours.Under the optimum condition,the dosage of the total of cellulose,hemicelluloses,lignin was reduced by 11.12%.However, such pretreatment did not led to an increase of anaerobic digestion efficiency and biogas yield from wheat straw.